Portable electric cutting device with blower mechanism

ABSTRACT

Fanned air generated by a fan to cool a motor is discharged from a housing through fanned air discharge ports toward an opening formed in a base. The fanned air discharged toward the opening is then introduced into a groove in fluid communication with the opening. The groove is formed in a bottom surface of the base and has an open side at a front side of the base. The fanned air is then discharged from the front side of the base, blowing off saw dust on a cutting object so as to prevent dust from accumulating on a marking line on the cutting object.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a portable electric cuttingmachine, and more particularly to a portable electric cutting machineprovided with an air-discharge mechanism for discharging air from ahousing into a saw blade housing section of a saw cover.

[0003] 2. Related Art

[0004] When cutting a cutting object, such as timber, by using aportable electric cutting machine (hereinafter referred to as “portableelectric circular saw”), a marking line is drawn on the cutting objectand then the object is cut along the marking line for the purpose ofimproving the cutting accuracy. More specifically, a guide piece forindicating the edge position of the saw blade is disposed at the frontend of a base so that the guide piece locates on an imaginary lineextended in a cutting direction from the saw blade. A user can cut thecutting object while directly confirming the positional relationshipbetween the blade edge of the saw blade and the marking line on thecutting object. Alternatively, the user can cut the cutting object whileindirectly confirming the positional relationship between the blade edgeof the saw blade and the marking line by aligning the guide piece withthe marking line.

[0005] However, when the bottom surface of the base slides on thecutting object, the marked line may be blurred or erased due to frictionbetween the bottom surface of the base and the upper surface of thecutting objects, disabling the user to confirm the positionalrelationship between the blade edge and the marking line. Also, if inkof the marking line transfers onto the bottom surface when sliding, thenthe ink may get back to the cutting object so that the cutting objectgets dirty.

[0006] Further, if a large volume of saw dust produced during thecutting operation piles on the cutting object, the marking line becomesinvisible. In this case, the user can no longer confirm the positionalrelationship between the blade edge of the saw blade and the markingline, resulting in degradation of cutting accuracy and decreasing incutting efficiency.

[0007] Saw dust accumulates on the cutting object when, for example, thesaw dust produced in the cutting operation flies up and then falls downon the cutting object. Therefore, it is conceivable to use a dustcollector for collecting saw dust generated during cutting operation,thereby preventing saw dust from flying up during the cutting operation.However, dust can be produced during, not only cutting operations, butalso other operations using various other tools. In this case, even ifsuch a dust collector is used during cutting operations, dust mayaccumulate on the cutting object to hide the marking line. In this case,a user needs to wipe off or blow off the dust on the cutting objectbefore starting a cutting operation so that the user can see the markingline. This reduces the efficiency of the cutting operation. Also, theuser needs to stop the cutting operation to remove saw dust which hasbeen generated and piled on the cutting object during the cuttingoperation. This reduces both the cutting accuracy and the efficiency ofthe cutting operation.

[0008] Japanese Utility Model registration No. 2607480 discloses aconventional portable electric circular saw, which includes a saw blade,a motor that drives the saw blade, a housing that houses the motor, asaw cover attached to the housing, a base linked to the housing, and afan. The saw cover has a saw blade housing section that houses the upperhalf of the outer periphery of the saw blade. The base has a bottomsurface that slides on the cutting object. The fan is driven by themotor for generating an air current (hereinafter referred to as “fannedair”) to cool the motor. A wall of the saw cover that is positionedbetween the fan and the saw blade housing section is formed with fannedair discharge ports for discharging the fanned air into the saw bladehousing section. The fanned air discharge ports are defined by aplurality of division walls.

[0009] Each division wall has a surface extending in parallel with arotary shaft of the fan and in a radial direction of the rotary shaft.Thus, as passing through the fanned air discharge ports, the fanned airis directed to flow in a direction parallel to the rotary shaft of thefan and then discharged into the saw blade housing section. The fannedair discharged into the saw blade housing section in this mannercollides with the lateral surface of the saw blade housed in the sawblade housing section and the lateral surface of a safety cover, whichis rotatably disposed so that the saw blade housing section can housethe safety cover during cutting operations. Then, the fanned airdiffuses along the lateral surfaces of the saw blade and the safetycover. The diffused fanned air is then discharged to the outside of thesaw cover through either between the inner wall of the saw cover and thesaw blade or between the inner wall of the saw cover and the safetycover. Since the fanned air collides with the lateral surfaces of thesaw blade and the safety cover substantially at a right angle, thecollided fanned air diffuses substantially uniformly across wide area ofthe surfaces. The fanned air may be discharged from the rear side of thesaw cover in the cutting direction due to air current, which is producedby rotation of the saw blade in the saw blade housing section.

[0010] The fan is a centrifugal fan. Fanned air generated by thecentrifugal fan flows outwardly in radial directions of the centrifugalfan, swirls along the inner wall of the housing, and then is dischargedinto the saw blade housing section through the fanned air dischargeports. The flow rate and the amount of the fanned air discharged throughthe fanned air discharge ports are higher in areas close to the rotaryaxis of the fan and lower in areas remote from the rotary axis withrespect to the radial directions of the fan. This arises a problem ofgeneration of noise in radially remote areas. This problem can beovercome by downsizing the fan or reducing the rotation speed of thefan. However, this results in reducing the flow rate of the fanned air,thereby degrading the cooling performance of the fan.

[0011] Japanese Utility Model Application-Publication No. SHO-55-154101discloses a portable electric circular saw that includes a cylindricalguide pipe disposed at the outside of a saw cover along a housing. Theguide pipe is in communication with fanned air discharge ports. Fannedair discharged from the fanned air discharge ports is guided through theguide pipe to the top surface of a cutting object and blows off saw dustfrom the cutting object. In this manner, the saw dust and other dust areprevented from accumulating on the cutting object.

[0012] However, the guide pipe becomes an obstacle when confirming thepositional relationship between the marking line and the blade edge ofthe saw blade, reducing the visibility of the marking line.Additionally, the assembling efficiency falls and the cost rises becauseof the increased number of the components.

[0013] When the cutting operation is performed, for example, in a closedarea with limited space or in a room with painted walls still wet,blowing the fanned air to disperse the saw dust may not be preferable.

SUMMARY OF THE INVENTION

[0014] In the view of foregoing, it is an object of the presentinvention to overcome the above problems, and also to provide a portableelectric circular saw that prevents the marking line from being blurredor erased during cutting operation, enabling a user to reliably confirmthe positional relationship between a blade edge of a saw blade and amarking line on a cutting object during the operations.

[0015] Another object of the present invention is to provide a portableelectric circular was that can effectively prevent accumulation of duston an cutting object by using fanned air generated for cooling a motorso as to improve cutting accuracy and cutting efficiency.

[0016] Still another object of the present invention is to provide aportable electric circular saw that can selectively prevent dust frombeing dispersed by the fanned air, without increasing the number ofcomponents.

[0017] Still another object of the present invention is to provide aportable electric circular saw that can suppress the generation of noisewithout reducing the cooling performance of the fan.

[0018] In order to attain the above and other objects, the presentinvention provides a portable electric cutting device including a sawblade that cuts a cutting object in a cutting direction, a casing thatpartially houses the saw blade, and a base linked to the casing. Thebase has a bottom surface that slides on the cutting object. The bottomsurface is formed with an opening through which the saw blade projectsdownward beyond the bottom surface. The bottom surface is formed with afirst groove extended forward in the cutting direction from a front endof the opening to a front end of the base. The first groove is in fluidcommunication with the opening and being opened to the front end of thebase.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In the drawings:

[0020]FIG. 1 is a schematic perspective view of a portable electriccircular saw according to a first embodiment of the present invention;

[0021]FIG. 2 is a schematic front view of the portable electric circularsaw according to the first embodiment of the preset invention;

[0022]FIG. 3 is a schematic cross sectional view of the portableelectric circular saw taken along a line III-III in FIG. 2;

[0023]FIG. 4 is a schematic plan view of the portable electric circularsaw of FIG. 1;

[0024]FIG. 5 is a schematic right-side view of the portable electriccircular saw according to the first embodiment of the present invention;

[0025]FIG. 6 is a schematic right-side view of portable electriccircular saw according to the first embodiment with a saw blade tiltedwith respect to a bottom surface of a base by 45 degree;

[0026]FIG. 7 is a schematic left-side view of the portable electriccircular saw according to the first embodiment;

[0027]FIG. 8 is a schematic left-side view of the portable electriccircular saw according to the first embodiment with the saw blade tiltedwith respect to the bottom surface of the base by 45 degree;

[0028]FIG. 9 is a schematic front view of the portable electric circularsaw according to the first embodiment with a shallow cutting depth;

[0029]FIG. 10 is a schematic left-side view of the portable electriccircular saw according to the first embodiment with a shallow cuttingdepth;

[0030]FIG. 11 is a schematic front view of the base of the portableelectric circular saw according to the first embodiment;

[0031]FIG. 12 is a schematic right-side view of the base of FIG. 11;

[0032]FIG. 13 is a schematic left-side view of the base of FIG. 11;

[0033]FIG. 14 is a schematic perspective view of the bottom surface ofthe portable electric circular saw according to the first embodiment;

[0034]FIG. 15 is a schematic front view of the saw cover of the portableelectric circular saw of the first embodiment;

[0035]FIG. 16 is a schematic rear view of the saw cover of FIG. 15;

[0036]FIG. 17 is a cross-sectional view of the saw cover taken along aline B-B in FIG. 16;

[0037]FIG. 18 is a schematic front view of the saw cover of FIG. 16;

[0038]FIG. 19 is a schematic cross-sectional view of the saw cover takenalong line a C-C in FIG. 18;

[0039]FIG. 20 is a schematic cross-sectional view of division walls ofthe saw cover taken along a line a-a in FIG. 16;

[0040]FIG. 21 is a schematic cross-sectional view of a division wall ofthe saw cover taken along a line b-b in FIG. 16;

[0041]FIG. 22 is a schematic cross-sectional view of a division wall ofthe saw cover taken along a line c-c in FIG. 16;

[0042]FIG. 23 is a schematic cross-sectional view of a division wall ofthe saw cover taken along a line d-d in FIG. 16;

[0043]FIG. 24 is a schematic cross sectional view of a division wall ofthe saw cover taken along a line e-e in FIG. 16;

[0044]FIG. 25 is a schematic perspective view of the portable electriccircular saw according to the first embodiment with the saw bladeremoved;

[0045]FIG. 26 is a schematic front view of the portable electriccircular saw according to the first embodiment with the saw bladeremoved and the saw cover pivoted relative to the base;

[0046]FIG. 27 is a schematic perspective view of the portable electriccircular saw according to the first embodiment with the saw bladeremoved and a safety cover pivoted to a position where the lower end ofthe safety cover does not project beyond the bottom surface of the base;

[0047]FIG. 28 is a schematic rear view of the portable electric circularsaw according to the first embodiment;

[0048]FIG. 29 is a schematic front view of a portable electric circularsaw according to a second embodiment of the present invention;

[0049]FIG. 30 is a schematic plan view of a principal part of theportable electric circular saw according to the second embodiment of thepresent invention;

[0050]FIG. 31 is a schematic right-side view of the principal part ofthe portable electric circular saw according to the second embodiment ofthe present invention;

[0051]FIG. 32 is a schematic rear view of a saw cover of the portableelectric circular saw according to the second embodiment of the presentinvention;

[0052]FIG. 33 is a schematic cross-sectional view of the saw cover takenalong a line D-D in FIG. 32;

[0053]FIG. 34 is a schematic perspective bottom view of the portableelectric circular saw according to the second embodiment of the presentinvention;

[0054]FIG. 35 is a schematic perspective bottom view of a portableelectric circular saw according to a third embodiment of the presentinvention;

[0055]FIG. 36 is a schematic bottom view of a portable electric circularsaw according to a fourth embodiment of the present invention with ashield member at a non-shielding position;

[0056]FIG. 37 is a schematic bottom view of the portable electriccircular saw according to the fourth embodiment of the present inventionwith the shield member at a shielding position;

[0057]FIG. 38 is a schematic cross sectional view of a portable electriccircular saw according to a fifth embodiment of the present inventionwith a shield member is a non-shielding position;

[0058]FIG. 39 is a schematic cross sectional view of the portableelectric circular saw according to the fifth embodiment of the presentinvention with the shield member at an adjusting position;

[0059]FIG. 40 is a schematic cross sectional view of the portableelectric circular saw according to the fifth embodiment of the presentinvention with the shield member at a shielding position;

[0060]FIG. 41 is a schematic cross sectional view of a portable electriccircular saw according to a sixth embodiment of the present inventionwith a guide piece fitted to a base with its non-shield side facingdownward;

[0061]FIG. 42 is a schematic perspective view of the guide piece of FIG.41 with the non-shield side facing downward;

[0062]FIG. 43 is a schematic cross sectional view of the portableelectric circular saw according to the sixth embodiment of the presentinvention with the guide piece fitted to the base with its shield sidefacing downward;

[0063]FIG. 44 is a schematic perspective view of the guide piece of FIG.43 with its shield side facing downward;

[0064]FIG. 45 is a schematic perspective view of a portable electriccircular saw according to a seventh embodiment of the present inventionwith a saw blade removed and a shield member at a non-shieldingposition;

[0065]FIG. 46 is a schematic perspective view of the portable electriccircular saw according to the seventh embodiment of the presentinvention with the saw blade removed and the shield member at ashielding position;

[0066]FIG. 47 is a schematic perspective rear view of the portableelectric circular saw according to the seventh embodiment of the presentinvention;

[0067]FIG. 48 is a schematic cross-sectional view of a saw cover of theportable electric circular saw according to the seventh embodiment ofthe present invention taken along a line corresponding to the line C-Cin FIG. 18;

[0068]FIG. 49 is a schematic perspective bottom-side view of a portableelectric circular saw according to an eighth embodiment of the presentinvention with a saw blade removed and a shield member at anon-shielding position;

[0069]FIG. 50 is a schematic perspective bottom-side view of theportable electric circular saw according to the eighth embodiment of thepresent invention with the saw blade removed and the shield member at ashielding position;

[0070]FIG. 51 is a schematic perspective rear-side view of the portableelectric circular saw according to the eighth embodiment of the presentinvention;

[0071]FIG. 52 is a schematic cross sectional view of a saw cover of theportable electric circular saw according to the eighth embodiment of thepresent invention taken along a line corresponding to the line C-C inFIG. 18;

[0072]FIG. 53 is a schematic rear view of a saw cover and a shieldmember at a non-shielding position of a portable electric circular sawaccording to a ninth embodiment of the present invention;

[0073]FIG. 54 is a schematic rear view of the saw cover and the shieldmember at a shielding position of the portable electric circular sawaccording to the ninth embodiment of the present invention; and

[0074]FIG. 55 is a schematic cross sectional view taken along a line E-Ein FIG. 53.

PREFERRED EMBODIMENTS OF THE PRESENT INVENTION

[0075] Next, portable electric circular saws according to embodiments ofthe present invention will be described with reference to theaccompanying drawings. First, a portable electric circular saw accordingto a first embodiment of the present invention will be described withreference to FIGS. 1-28.

[0076] (1) Basic Configuration

[0077] As shown in FIGS. 1-3, the portable electric circular saw of thepresent embodiment includes a motor 1, a housing 2, a handle 3, a sawblade 4, a saw cover 5, a base 6, and a fan 7. The motor 1 drives thesaw blade 4 to rotate. The housing supports and houses the motor 1. Thehandle 3 is formed integral with the housing 2 or linked to the housing2 as a separate member. A user can turn ON and OFF the motor 1 throughoperation on a switch 3 a of the handle 3. The saw cover 5 is attachedto the housing 2 and has a saw blade housing section 5 a. The saw blade4 has a fan-side lateral surface facing the fan 7 and ahousing-section-side lateral surface facing the saw blade housingsection 5 a. The saw blade housing section 5 a partially houses theupper half peripheral portion of the saw blade 4 and the fan-sidelateral surface of the saw blade 4. The base 6 is linked to the housing2 by the saw cover 5 and has a bottom surface 6 a that slides on acutting object. The base 6 is formed with an opening 6 b through whichthe saw blade 4 is projected downward beyond the bottom surface 6 a. Thefan 7 is fixed to an output shaft 1 a of the motor 1 so that the fan 7rotates as the motor 1 drives to rotate. The rotation of the fan 7generates fanned air to cool the motor 1. As shown in FIG. 15, fannedair discharge ports 5 c are formed in a wall of the saw cover 5 locatedbetween the fan 7 and the saw blade housing section 5 a for dischargingthe fanned air from the housing 2 into the saw blade housing section 5a. The fanned air discharge ports 5 a are defined by a plurality ofdivision walls 5 d.

[0078] As shown in FIG. 3, one end of the housing 2 is formed with anair intake port 2 a, through which internal space of the housing 2 is influid communication with external space. Rotation of the fan 7 draws airinto the housing 2 through the air intake port 2 a The air passes by theouter periphery of the motor 1 as the fanned air and cools the motor 1.That is, the fan 7 is provided to cool the motor 1 with fanned air. Itshould be noted that the fan 7 rotates in a direction indicated by anarrow D in FIG. 2 (hereinafter referred to as “rotation direction D”).

[0079] A pinion gear 8 is disposed at an end of the output shaft 1 a ofthe motor 1. The pinion gear 8 may be formed integral with the outputshaft 1 a or as a component separated from the output shaft 1 a. Thepinion gear 8 is in a meshing engagement with a gear 9 that is rotatablysupported by the saw cover 5. The gear 9 is fixed to a drive shaft 10that is coaxial with the gear 9 so that the gear 9 rotates together withthe rotation of the drive shaft 10. The drive shaft 10 is rotatablysupported by the saw cover 5 via bearings 11, 12, which are coaxial withthe gear 9 and sandwich the gear 9 therebetween. A pair of saw bladelocking members 13 are attached to the drive shaft 10. The saw bladelocking members 13 are not rotatable relative to the drive shaft 10 andpinch the saw blade 4 therebetween. With this configuration, the drivingpower of the motor 1 is transmitted via the output shaft 1 a, the piniongear 8, the gear 9, the drive shaft 10, and the saw blade lockingmembers 13 to the saw blade 4, enabling the saw blade 4 to cut thecutting object. Here, while transmitting the driving power of the motor1 to the saw blade 4, the pinion gear 8 and the gear 9 reduce thedriving power by a certain degree. The rotation direction of the sawblade 4 is opposite to the rotation direction D of the fan 7.

[0080] The portable electric circular saw further includes a safetycover 17 supported by the drive shaft 10 coaxially with the same. Thesafety cover 17 covers substantially a half of the outer periphery ofthe saw blade 4 and can be contained in the saw blade housing section 5a. The safety cover 17 has a lever 17 a. The safety cover 17 is urged byan urging member (not shown), such as a spring. FIG. 1 shows the initialstate of the safety cover 17, where the most part of the safety cover 17projects downward beyond the bottom surface 6 a of the base 6 so as toprevent the outer periphery of the saw blade 4 from being exposed. Whena cutting operation is conducted, the front end (right end in FIG. 2) ofthe safety cover 17 abuts the rear end of the cutting object. As theuser slides the portable electric circular saw on the cutting object inthe cutting direction, the safety cover 17 rotates and enters the sawblade housing section 5 a against the urging force of the urging member,exposing the saw blade 4 at the bottom surface 6 a of the base 6. In thecase of cutting out a piece from the cutting object without cutting anyedges of the cutting object, the user can rotate the safety cover 17 byoperating the lever 17 a to expose the saw blade 4 at the bottom.

[0081] The saw cover 5 has a pinion gear housing section 5 e in asubstantially circular shape for housing the pinion gear 8. A bearing 14for rotatably supporting the pinion gear 8 is press-fitted to the sawcover 5 so as to place the pinion gear 8 substantially at the center ofthe pinion gear housing section 5 e.

[0082] A side surface of the saw cover 5 is attached to the 1.5 sidesurface of the housing 2 by screws 15. The pinion gear housing section 5e is disposed between the saw blade housing section 5 a and the housing2 for housing the gear 9 therein. That is, the space between the sawblade housing section 5 a and the housing 2 serves as a gear casing. Asshown in FIG. 2, the saw cover 5 is linked to the base 6 such that thesaw cover 5 sandwiches the saw blade 4 at the front and rear ends of thebase 6. A saw blade inclination regulating mechanism and a saw bladecutting depth regulating mechanism are arranged at the link section.

[0083] (2) Saw Blade Inclination Regulating Mechanism

[0084] The saw blade inclination regulating mechanism includes a frontinclination regulating mechanism located near the front end of the base6 as viewed in the cutting direction and a rear inclination regulatingmechanism located near the rear end of the base 6. As shown in FIG. 1,the front inclination regulation mechanism includes a rotary shaft 20, ahinge holding section 21, a bevel plate 23, and a bolt 24, whereas therear inclination regulating mechanism includes a pin 25, a link 26, abolt 27, a bevel plate 28, and a bolt 29.

[0085] First, the front inclination regulating mechanism will bedescribed with reference to FIGS. 1 and 4-6. The pin 22 is rigidlyfitted to the base 6 at a position near the front end of the base 6 inthe cutting direction. The pin 22 extends in a direction perpendicularto the rotary shaft of the saw blade 4. The pin 22 serves as a firstfulcrum of inclination. The bevel plate 23 extends substantially inparallel with the front edge of the base 6 and in the upward directionfrom the base 6. The bevel plate 23 is formed with an arc-shaped throughhole 23 a on an imaginary circular line centered at the axial center ofthe pin 22. The hinge holding section 21 is rotatable about the pin 22both rightward and leftward relative to the base 6. The hinge holdingsection 21 is engaged with the bolt 24 that is inserted through thethrough hole 23 a-The angular position of the hinge holding section 21is fixed by tightening the bolt 24. That is, the user can loose the bolt24 and lift up the housing 2, rotating the hinge holding section 21about the pin 22, to bring the hinge holding section 21 from the postureshown in FIG. 5 into the inclined posture shown in FIG. 6. The user canmaintain the inclined posture of the hinge holding section 21 bytightening the bolt 24.

[0086] The hinge holding section 21 has a substantially U-shape thatpinches the front end of the saw cover 5 from the right and the left(FIG. 4). The rotary shaft 20 is rotatably supported by the hingeholding section 21. The saw cover 5 is formed with a hole 5 f at thefront portion (FIG. 15) that extends substantially in parallel with therotary shaft of the saw blade 4. The rotary shaft 20, which is rotatablysupported by the hinge holding section 21, is inserted into the hole 5f, so that the saw cover 5 can pivot up and down about the rotary shaft20 relative to the hinge holding section 21.

[0087] Next, the rear inclination regulating mechanism will be describedwith reference to FIGS. 7 and 8. The pin 25 extends in a directionsubstantially parallel to the upper surface of the base 6 andperpendicular to the rotary shaft of the saw blade 4. The pin 25 servesas a second fulcrum of inclination. The pins 25 and 22 are arranged suchthat a virtual line connecting the pin 25 and the pin 22 extendssubstantially in parallel with the lateral surfaces of the saw blade 4.The link 26 is linked to the pin 25 and pivotable about the pin 25 tothe right and the left of the base 6. The bevel plate 28 extendssubstantially in parallel with the rear edge of the base 6 and protrudesupward from the base 6. The bevel plate 28 is formed with an arc-shapedthrough hole 28 a on an imaginary circular line centered at the pin 25.The link 26 is engaged with the bolt 29 that is inserted through thethrough hole 28 a so that the angular position of the link 26 is fixedby tightening the bolt 29.

[0088] As mentioned above, the saw cover 5 and the base 6 are linked toeach other by the pins 22 and 25 serving as the first and secondfulcrums. With this configuration, the saw cover 5 can pivot relative tothe base 6 about the pins 22 and 25. This inclination of the saw cover 5inclines the saw blade 4 relative to the bottom surface 6 a of the base6. FIGS. 6 and 8 schematically indicate the saw cover 5 pivoted aboutthe pins 22 and 25 so that the lateral surfaces of the saw blade 4 tiltswith respect to the bottom surface 6 a of the base 6 by 45 degree, whichis the maximum angle in the present embodiment,

[0089] The hinge holding section 21 and the link 26 can pivot within arange defined by the holes 23 a, 28 a of the bevel plates 23, 28. Inother words, the hinge holding section 21 pivots along the wall surfacesof the bevel plate 23, 28 that face the saw blade 4 (rear side surfaceof the bevel plate 23 and the front side surface of the bevel plate 28).These wall surfaces of the bevel plates 23, 28 (in particular the wallsurface of the bevel plate 23) are machined to improve the planaraccuracy, and the hinge holding section 21 and the link 26 are designedto partially abut the wall surfaces of the bevel plates 23, 28, so as toensure the accurate positional relationship between the saw cover 5 andthe base 6 when pivoted about the pin 22 and the pin 25.

[0090] Because the handle 3 is located remote from the saw blade 4, theload applied to the handle 3 operates to pivot the saw cover 5 and thehousing 2 relative to the base 6. Therefore, it is preferable that thebevel plate 23 and the bevel plate 28 are arranged near the front andrear ends of the base 6, respectively, as viewed in the cuttingdirection as described above. This arrangement can prevent the cuttingdepth from unintentionally and abruptly changed, and effectively preventthe angle (orientation) of the saw blade 4 from being accidentallychanged due to a load applied to the portable electric circular saw,securing positional accuracy of the pivoted saw blade 4. However, onlyone of the bevel plates may be provided. For example, only the bevelplate 23 may be arranged near the front end of the base 6

[0091] Usually, the pins 22, 25 serving as fulcrums are located close toan imaginary line that extends through the front and rear edges of thesaw blade 4. With this configuration, a position from which the tiltingsaw blade 4 projects downward beyond the bottom surface 6 a of the base6 does not significantly differ from a position from which the uprightsaw blade 4 projects downward. Also, a large cutting depth can besecured when the cutting operation is performed with the tilting sawblade 4 (slant cut).

[0092] (3) Saw Blade Cutting Depth Regulating Mechanism

[0093] As described above, the saw cover 5 can pivot about the rotaryshaft 20, upward and downward relative to the hinge holding section 21.The link 26 is linked to the pin 25 at a lower part thereof. As shown inFIG. 10, the upper part of the link 26 can be housed inside the sawblade housing section 5 a and is provided with a link guide 26A having ashape corresponding to the upper inner wall of the saw blade housingsection 5 a. The link guide 26A is formed with alongitudinally-extending long hole 26 a at the upper section. A cuttingdepth regulating bolt 27 is fitted to the saw cover 5 through the longhole 26 a. Tightening the bolt 27 fixes the position of the link guide26A relative to the saw cover 5.

[0094] With this configuration, the saw cover 5 can pivot relative tothe base 6 about the rotary shaft 20. Pivoting movement of the saw cover5 changes the amount of the saw blade 4 projecting beyond the bottomsurface 6 a of the base 6, i.e., the cutting depth. The cutting depthcan be fixed by tightening the bolt 27. FIGS. 9 and 10 indicate the sawcover 5 pivoted clockwise about the rotary shaft 20 so that the linkguide 26A exposes from the rear end of the saw cover 5.

[0095] (4) Laser Unit

[0096] The saw blade housing section 5 a of the saw cover 5 has ahousing-side outer wall that faces the housing 4. As shown in FIGS. 4-6,a laser unit 34 is disposed on the housing-side outer wall of the sawblade housing section 5 a. The laser unit 34 includes light irradiationdevices 34 a, 34 b. As shown in FIG. 18, the housing-side outer wall ofthe saw blade housing section 5 a is formed with a recess 5 i having aplane section 5 ia extending substantially in parallel with the lateralsurfaces of the saw blade 4. As shown in FIG. 16, the plane section 5 iais formed with a pair of threaded holes 5 ib. The laser unit 34 isattached to the plane section 5 ia by a screw 35 (FIG. 28) such that thesurface of the light irradiation device 34 a contacts the surface of theplane section 5 ia. The light irradiation device 34 a includes two LEDs34 aa that emit laser beams to illuminate the edge position of the sawblade 4 at the front end of the base 6 and at a spot ahead of the frontend as viewed in the cutting direction. The light irradiation device 34b projects from the lower front end of the saw cover 5 toward the base 6(FIGS. 25, 28). The light irradiation device 34 b includes LEDs (notshown) that emit laser beams in a direction inclined with respect to thelateral surfaces of the saw blade 4. The ON/OFF control of the laserunit 34 is performed by a user operating on switches 3 b provided to thehandle 3. The laser unit 34 is supplied with power from a power sourceof the portable electric circular saw.

[0097] Positional accuracy is required when arranging the laser unit 34,the light irradiation device 34 a in particular. According to thepresent embodiment, the light irradiation device 34 a can easily andaccurately be positioned due to the external profile of the planesection 5 ia of the saw cover 5 and that of the laser unit 34. Hence,the assembling operation can be conducted highly efficiently. Note that,as shown in FIGS. 5 and 6, the hinge holding section 21 that is locatedon an irradiation path of the laser light from the LED 34 aa is formedwith a recess 21 a so as not to block the laser beams.

[0098] (5) Base

[0099] Next, the base 6 will be described in detail with reference toFIGS. 11-14.

[0100] The above-described bevel plates 23, 28 are arranged near thefront and rear ends of the base 6, respectively. Each bevel plate 23, 28extends along the corresponding one of the front and rear edges of thebase 6. The bevel plate 23, 28 is arranged in an upright posture so asto extend in a direction perpendicular to the bottom surface 6 a of thebase 6. Projecting parts 30, 32 are formed integrally with the bevelplates 23, 28, respectively, to project from the base 6 and support thecorresponding ones of the pins 22, 25 that serve as linking sections forlinking the base 6 and the saw cover 5. More specifically, as shown inFIG. 12, the projecting part 30 is formed with a hole 31 in which thepin 22 is supported. On the other hand, the projecting part 32 is formedwith a hole 33 in which the pin 25 is supported. The central axes of theholes 31, 33 are aligned with each other in a direction substantiallyparallel to the surfaces of the saw blade 4.

[0101] Alternatively, it is possible to use a pair of projecting parts30 each formed with the hole 31. The projecting parts 30 are arrangedside by side in the axial direction of the pin 22. The pin 22 issupported between the projecting parts 30, and the hinge holding section21 is disposed between the projecting parts 30. This configurationprevents deformation of the pin 22 that is linked to the hinge holdingsection 21. Accordingly, even if the user applies excess pressure to thesaw cover 5 via the handle 3 during cutting operations, change incutting depth and the angle of the saw blade 4 can be suppressed.

[0102] As shown in FIG. 14, the bottom surface 6 a of the base 6 isformed with a groove 6 c at a front position as viewed in the cuttingdirection. The groove 6 c is in fluid communication with the opening 6 band extends to the front end of the base 6. In the state shown in FIG.9, the groove 6 c is located on an imaginary line that extends forwardin the cutting direction from the front edge of the saw blade 4 in theupright posture and has a width greater than the thickness of the bladeedge of the saw blade 4. The width of the groove 6 c is sufficientlylarge so that even an imaginary line that extends in the cuttingdirection from an intersection between the saw blade 4 tilting by themaximum angle of 45 degree and the bottom surface 6 a of the base 6 isfound within the groove 6 c (see FIG. 6). As shown in FIG. 12, the depthof the groove 6 c is less than a half of the thickness of the base 6.

[0103] As shown in FIGS. 1, 4 and 5, the guide piece 16 for indicatingthe edge position of the saw blade 4 is detachably attached to the topsurface of the base 6 by a screw 18, at a position corresponding to thefront part of the groove 6 c. The guide piece 16 includes a guidesection 16 a and a guide section 16 b. The guide section 16 a indicatesthe edge position of the saw blade 4 in the upright posture where thesurfaces of the saw blade 4 extend perpendicular to the bottom surface 6a of the base 6. The guide section 16 b indicates the edge position ofthe saw blade 4 that is tilted by 45 degree with respect to the bottomsurface 6 a of the base 6.

[0104] The bottom surfaces of the guide sections 16 a, 16 b projectdownward to be flush with the bottom surface 6 a of the base 6, whereasthe bottom surface of the guide piece 16 except the guide sections 16 a,16 b is substantially flush with the top surface of the groove 5 c. Withthis arrangement, the guide section 16 a or 16 b can be easily alignedwith the marking line drawn on the cutting object. Also, because thebottom surface of the guide piece 16 except the guide sections 16 a, 16b is substantially flush with the top surface of the groove 6 c, an airpathway is defined between the bottom surface of the guide piece 16 andthe upper surface of the cutting object for allowing air to passtherethrough. Note that as long as the air pathway is establishedbetween the bottom surface of the guide piece 16 and the cutting object,it is unnecessary to make the bottom surface of the guide piece 16 to beflush with the top surface of the groove 6 c.

[0105] As described above, the groove 6 c is formed on the imaginaryline extended forward in the cutting direction from the front edge ofthe saw blade 4. Therefore, even when the bottom surface 6 a of the base6 slide on the upper surface of a cutting object during cuttingoperation, the bottom surface 6 a does not contact the marking linedrawn on the upper surface of the cutting object. Accordingly, there isno danger that the marking line is blurred or erased, enabling accuratecutting operation. Also, because the bottom surface 6 a does not contactthe marking line, the ink of the marking line will not transfer to thebottom surface 6 a, ensuring the cutting object stay clean.

[0106] As described above, the groove 6 c is formed on the imaginaryline extended in the cutting direction from the front edge of the sawblade 4, and the pin 22 is arranged near the imaginary line. In otherwords, the pin 22 locates vertically above the groove 6 c on the base 6(FIG. 12). The projecting part 30 formed with the hole 31 for holdingthe pin 22 on the base 6 extends from where the groove 6 c is formed andto where the groove 6 c is not formed (near the left edge of the bevelplate 23). With this configuration, even when a user applies excessivepressure onto the saw cover 5 via the handle 3 during cuttingoperations, the projecting part 30 prevents the base 6 from beingdeformed, particularly in an area near the groove 6 c. Also, areinforcement rib 6 e is provided on the base 6 to extend from where thegroove 5 c is formed to where the groove 6 c is not formed and toprotrude upward from the base 6 and continues from the projecting part30. This reinforcement rib 6 e strengthens the base 6 whose strength hasbeen reduced in an area around the groove 6 c due to the presence of thegroove 6 c. The reinforcement rib 6 e may be formed either continuouslywith or independent from the projecting part 30.

[0107] As shown in FIG. 14, the base 6 is formed further with a hole 6 din fluid communication with the groove 6 c. This hole 6 d is formedduring the machining operation for raising the planar accuracy of thesaw-blade-side surface of the projecting part 30. Since the pin 22locates near the top surface of the base 6, a lower part of the hingeholding section 21 projects downward beyond the top surface of the base6 through the hole 6 d. In other words, the hole 6 d serves as a housingthat houses the lower part of the hinge holding section 21.

[0108] (6) Blower Mechanism

[0109] Next, a blower mechanism that utilizes fanned air produced by thefan 7 will be described with reference to FIGS. 3 and 15-28. As shown inFIG. 3, the gear casing part of the saw cover 5 has a width equal to orgreater than the width of the gear 9 in the axial direction of theoutput shaft 1 a. As shown in FIG. 15, the gear casing part is formedwith the fanned air discharge ports 5 c at a position radially outwardfrom the pinion gear 8. The fanned air discharge ports 5 c leads thefanned air, that has flown through the housing 2 and cooled the motor 1,from the housing 2 into the saw blade housing section 5 a.

[0110] The fanned air discharge ports 5 c are defined by a plurality ofdivision walls 5 d arranged in the saw cover 5. The division walls 5 dmay be formed either integrally with or separate from the saw cover 5.As shown in FIG. 3, each division wall 5 d has the width L1 that isabout ⅓ of the width L of the gear casing part of the saw cover 5 in theaxial direction of the output shaft 1 a. The fanned air discharge ports5 a have a radial dimension that allows the outer peripheries of thevanes of the fan 7 to be located within the fanned air discharge ports 5c with respect to the radial direction of the output shaft 1 a.

[0111] In this embodiment, a total of seven division walls 5 d areprovided. As shown in FIGS. 15 and 16, the fanned air discharge ports 5c are arranged radially about the rotation center C1 of the fan 7. Morespecifically, the division walls 5 d include division walls 5 da 1, 5 da2, 5 da 3, 5 db, 5 dc 1, 5 dc 2, and 5 dc 3 arranged in this order fromthe upstream side in the rotation direction D of the fan 7. A singlefanned air discharge port 5 c is defined between two adjacent divisionwalls 5 d. Since the division walls 5 da 1, 5 da 2, and the like extendsubstantially in parallel with the rotation axis of the fan 7, only theend surfaces of these division walls are shown in FIGS. 15 and 19, andthe fanned air discharge ports 5 c are shown as the gaps between thedivision walls. On the other hand, because the division walls 5 db, 5 dc1, and the like each has a part (guide portion to be described later)that is not in parallel with the rotation axis of the fan 7, not onlythe end surfaces but also the guide portions of these division walls areshown in FIGS. 15 and 19. Therefore, the guide portions and also thefanned air discharge ports 5 c are shown between the adjacent divisionwalls in these drawings.

[0112] The division walls 5 d are divided into three different groups.The first group includes the division walls 5 da 1, 5 da 2, and 5 da 3located at the upstream side in the rotation direction D of the fan 7and rear of both the rotation center C1 of the fan 7 and the rotationcenter C2 of the saw blade 4 in the cutting direction. As shown in FIG.20, these division walls 5 da 1-5 da 3 extend substantially in parallelwith in the rotary shaft of the fan 7 for discharging fanned air in thedirection substantially parallel to the rotary shaft of the fan 7.

[0113] The second group of the division walls 5 includes the divisionwalls 5 dc 1, 5 dc 2, and 5 dc 3 located downstream side in the rotationdirection D of the fan 7. The division walls 5 dc 1-5 dc 3 are locatedin front of the rotation center of C1 of the fan 7 and the rotationcenter C2 of the saw blade 4 with respect to the cutting direction. Asshown in FIGS. 22-24, the division walls 5 dc 1-5 dc 3 include flow ratereducing parts 5 dc 1 a, 5 dc 2 a, 5 dc 3 a extending in the directionsubstantially parallel to the rotation axis of the fan 7 and guidingparts 5 dc 1 b, 5 dc 2 b, 5 dc 3 b extending aslant from the flow ratereducing parts 5 dc 1 a-5 dc 3 a. The flow rate reducing parts 5 dc 1a-5 dc 3 a are arranged at the fan side, whereas the guiding parts 5 dc1 b-5 dc 3 b are arranged at the saw-blade-housing-section side. Thedivision walls 5 dc 1-5 dc 3 discharges fanned air forward in thecutting direction.

[0114] The third group includes the division wall 5 db that is locatedbetween the first group (division walls 5 da 1-5 da 3) and the secondgroup (division walls 5 dc 1-5 dc 3) in the rotation direction D of thefan 7. The division wall 5 db is disposed substantially vertically abovethe rotation center C2 of the saw blade 4. As shown in FIG. 21, thedivision wall 5 db includes a flow rate reducing part 5 dba extendingsubstantially in parallel with the rotary axis of the fan 7 and aguiding part 5 dbb extending aslant from the flow rate reducing part 5dba. The flow rate reducing part 5 dba has a length substantially thesame as that of the division walls 5 dc 1-5 dc 3 in the directionparallel to the rotary axis of the fan 7.

[0115] The guiding parts 5 dbb, 5 dc 1 b, 5 dc 2 b, and 5 dc 3 b of thedivision walls 5 d each has an upstream-side wall surface that facesupstream side with respect to the rotation direction D of the fan 7. Theupstream-side wall surface extends aslant from a housing-side end of thecorresponding flow rate reducing part 5 dba, 5 dc 1 a, 5 dc 2 a, 5 dc 3a, toward the downstream in the rotation direction D. The housing-sideend is the end close to the saw blade housing section 5. The angle ofthe upstream-side wall surfaces of the guiding parts 5 dbb and 5 dc 1b-5 dc 3 b with respect to the upstream-side wall surfaces of thecorresponding flow rate reducing part 5 dba and 5 dc 1 a-5 dc 3 a is 45degree. In the division wall 5 dc 1-5 dc 3, the boundary between theupstream-side wall surface of the flow rate reducing part 5 dc 1 a-5 dc3 a and the upstream-side wall surface of the reducing part 5 dc 1 b-5dc 3 b is not chamfered to show an arc-shaped profile, but is left inangular shape.

[0116] As shown in FIGS. 15 and 16, the division walls 5 da 1-5 da 3,the flow rate reducing part 5 dba of the division wall 5 db, and theflow rate reducing parts 5 dc 1 a-5 dc 3 a of the division walls 5 dc1-5 dc 3 are arranged to incline 45 degree (angle è shown in FIG. 15)with respect to the radial directions of the rotary axis of the fan 7(rotation center C1) such that the radially outer ends of the divisionwalls 5 da 1-5 da 3 and the flow rate reducing parts 5 dba and 5 dc 1a-5 dc 3 a are located upstream from the radially inner ends thereofwith respect to the rotation direction D of the fan 7.

[0117] A wall 5 h is disposed at the downstream side of the divisionwall 5 dc 3 in the rotation direction D, defining a fanned air dischargeport 5 c therebetween. Similar to the division wall 5 da 1 and the like,an upstream-side wall surface of the wall 5 h is inclined from theradial direction of the rotary axis of the fan 7 so that the radiallyouter end of the wall 5 h locates downstream from the radially inner endof the wall 5 h with respect to the rotation direction D. Thehousing-section-side edge surface of the guiding part 5 dc 3 b of thedivision wall 5 dc 3 extends substantially in parallel with the wallsurface of the wall 5 h.

[0118] As shown in FIGS. 15 and 26, the division walls 5 d are formedsuch that a user can see the other side of the division walls 5 dthrough the discharge ports 5 c when viewed from the front side of thesaw cover 5, i.e, from the saw blade housing section 5 a side or fromthe left side in FIG. 3. More specifically, the division wall 5 db andthe division wall 5 dc 1 define, therebetween, a gap that extend in thedirection parallel to the rotary axis of the fan 7. In other words, thedivision wall 5 db does not overlap with the division wall 5 dc 1 withrespect to the direction parallel to the rotary axis of the fan 7. Thedivision wall 5 dc 2 and its adjacent division wall 5 dc 3 show thesimilar relationship, and so do the other division walls 5 d. With thisarrangement, the saw cover 5 can be formed by molding. The surfacesdefining these gaps between adjacent division walls 5 d are insubstantially parallel with each other with respect to the radialdirection of the rotary axis of the fan 7.

[0119] When the saw cover 5 is viewed from the front side thereof (leftside in FIG. 3), the housing-section-side end surface of each of theguiding parts 5 dbb, 5 dc 1 b, 5 dc 2 b of the division walls 5 db, 5 dc1, 5 dc 2 is in substantially parallel with the housing-section-side endsurface of corresponding one of the flow rate reducing parts 5 dc 1 a, 5cd 1 a, and 5 dc 3 a of the adjacent division walls 5 dc 1, 5 dc 2, and5 dc 3. Therefore, for example, the angle between the guiding part 5 dbband the flow rate reducing part 5 dba at a radially inner area differsfrom the angle at a radially outer area. The same is true for theguiding part 5 dc 1 b and the flow rate reducing part 5 dc 1 a, theguiding part 5 dc 2 b and the flow rate reducing part 5 dc 2 a, and theguiding part 5 dc 3 b and the flow rate reducing part 5 dc 3 a. Withthis arrangement, the spaces between the adjacent division walls 5 d canbe utilized effectively to define the fanned air discharge paths 5 cthrough which fanned air is discharged forward in the cutting direction.Here, each guiding part 5 dbb, 5 dc 1 b, 5 dc 2 b has a continuoussurface.

[0120] As shown in FIGS. 19 and 25-27, a step 5 g projecting toward thesaw blade 4 is formed on the inner wall of the saw blade housing section5 a at a position between the fanned air discharge ports 5 c and thelower front end of the saw cover 5 with respect to the cuttingdirection. The step 5 g is the rear side of the above-described recess 5i. That is, the step 5 g is formed when the recess 5 i is formed. Thestep 5 g is formed such that the lower end of the step 5 g locates rearof the front end of the opening 6 b of the base 6 in the cuttingdirection even when the saw blade 4 is pivoted forward as shown in FIG.26 to reduce the cutting depth.

[0121] As shown in FIG. 27, the front end of the safety cover 17 in thepivoting direction (clockwise direction in FIG. 27) can come intoabutment with the step 5 g in the saw blade housing section 5 a. In thismanner, the step 5 g prevents the safety cover 17 from being pivoted inthe pivoting direction by more than a predetermined amount.

[0122] In FIG. 3, the fan 7 is a centrifugal fan, and hence fanned airis blown out in radial directions of the fan 7. A fan guide 19 in thehousing 2 makes the fanned air flow along the inner wall of the housing2, and the fanned air flows into the fanned air discharge ports 5 cwhile whirling. After entering the fanned air discharge ports 5 c, thefanned air is decelerated by striking the upstream-side wall surfaces ofthe division walls 5 da 1-5 da 3, the upstream-side wall surface of theflow rate reducing part 5 dba of the division wall 5 db, and theupstream-side wall surfaces of the flow rate reducing parts 5 dc 1 a-5dc 3 a of the division walls 5 dc 1-5 dc 3. Then, the fanned air flowsalong the wall surfaces through the fanned air discharge ports 5 c andis discharged into the saw blade housing section 5 a. Especially, thefanned air struck the flow rate reducing parts 5 dc 1 a-5 dc 3 a isdischarged into the saw blade housing section 5 a after flowing alongthe wall surfaces of the guide parts 5 dc 1 b-5 dc 3 b that are incontinuous with the flow rate reducing parts 5 dc 1 a-5 dc 3 a. At thistime, because the division walls 5 da 1-5 da 3 and the flow ratereducing parts 5 dba and 5 dc 1 a-5 dc 3 a are inclined with respect tothe radial directions of the rotary shaft of the fan 7, the fanned airis discharged into the saw blade housing section 5 a while whirlingaround the rotation center C1 of the fan 7 in the rotation direction Dand being directed radially inward. Because the fanned air whirlsradially and inwardly in this manner, the flow rate and the amount ofthe fanned air being discharged from the fanned air discharge ports 5 cinto the saw blade housing section 5 a is smaller in a radially outerarea and larger in a radially inner area. Therefore, noise generated inthe radially outer area of each fanned air discharge port 5 c issuppressed while securing a sufficient flow amount by raising the flowamount in the radially inner area, which in turn secures the flow amountinto the opening 6 b and thus into the groove 6 c as will be describedlater.

[0123] It should be noted that these effects can be obtained only byarranging the division walls 5 d to have upstream-side wall surfacesthat tilt from the radial directions of the rotary shaft of the fan 7and that extend in a direction opposite to the rotation direction D.However, in this embodiment, the downstream-side wall surfaces of thedivision walls 5 d (particularly, the downstream-side wall surfaces ofthe flow rate reducing parts 5 dc 1 a-5 dc 3 a of the division walls 5dc 1-5 dc 3, and the downstream-side wall surface of the flow ratereducing part 5 dba of the division wall 5 db) also tilt with respect tothe radial direction to extend opposite to the rotation direction D asshown in FIGS. 20-24. Therefore, the upstream-side wall surfaces aresubstantially in parallel with the downstream-side wall surfaces. Thisarrangement secures the sufficient space for the air discharge ports 5 cand, at the same time, enables to form the fanned air discharge ports 5c in a shape that inclines with respect to the rotary shaft of the fan7. This in turn makes either to discharge the fanned air along theguiding parts into the saw blade housing section 5 a and forward in thecutting direction.

[0124] Since the upstream-side wall surfaces of the guiding parts 5 dbband 5 dc 1 b-5 dc 3 b are tilted with respect to the rotary shaft of thefan 7 such that the housing-section side ends locate downstream from thefan-side ends with respect to the rotation direction D, the fanned airthat has flown along the guiding parts 5 dbb and 5 dc 1 b-5 dc 3 b isdirected forward in the cutting direction and discharged into the sawblade housing section 5 a. The discharged fanned air strikes thefan-side lateral surface of the safety cover 17 in the saw blade housingsection 5 a (FIG. 27) and the fan-side lateral surface of the saw blade4 (FIG. 25) at an angle and flows along these lateral surfaces. Most ofthe fanned air flows along these lateral surfaces toward the rotaryshaft 20 as viewed from the rotation center C1 (FIG. 15). Some of thefanned air that has flown along the lateral surfaces of the safety cover17 and the saw blade 4 flows toward the opening 6 b of the base 6.

[0125] As the cutting depth is increased, the section of the saw blade 4that contacts the cutting object also increases with respect to thecutting direction. In this case, the saw blade 4 blocks more fanned airand prevents the same from flowing to the side of the saw blade 4opposite from the housing 2 (the front side of the drawing sheet of FIG.2 or left side in FIG. 3) through the space between the front edge ofthe saw blade 4 and the cutting object. Therefore, the fanned air isdirected toward the opening 6 b of the base 6 more effectively.Particularly, when the cutting depth is nearly the maximum as shown inFIG. 2, the fanned air is most likely to flow into the opening 5 b ofthe base 6. Also, when the cutting depth is nearly the maximum and thesafety cover 17 has been pivoted to be housed in the saw cover 5 asshown in FIG. 27, most of the fanned air discharged into the saw bladehousing section 5 a strikes the fan-side lateral surface of the safetycover 17, diffuses along the lateral surface, and flows frontward in thecutting direction. Some of the diffused air is discharged from the rearend of the saw cover 5 in the cutting direction after passing throughbetween the saw blade housing section 5 a and the safety cover 17. Theair discharged from the rear end blows onto the rear part of the base 6,preventing accumulation of saw dust in this part.

[0126] As shown in FIG. 27, the safety cover 17 has a curving edge 17 bdefining a cutout part that prevents the safety cover 17 from coveringthe entire fanned air discharge ports 5 c even when the safety cover 17is held in contact with the step 5 g as shown in FIG. 27. This allowsthe fanned air struck and flown along the lateral surface of the safetycover 17 and the fanned air directly discharged from the fanned airdischarge ports 5 c to flow smoothly toward the opening 6 b of the base6.

[0127] On the other hand, when the saw cover 5 is pivoted upward aboutthe rotary shaft 20 as shown in FIG. 26 to decrease the cutting depth,some of the fanned air discharged from the fanned air discharge ports 5c flows along the lateral surface of the saw blade 4 into the opening 6b of the base 6, whereas the remaining fanned air strikes the step 5 g.The fanned air struck the step 5 g flows downward along the step 5 g andthen forward in the cutting direction to the opening 6 b of the base 6.

[0128] The fanned air discharged into the opening 6 b in this mannerstrikes the top surface of the cutting object and blows off the saw dustthereon, preventing saw dust from accumulating on and near theintersection of the edge of the saw blade 4 and the bottom surface 6 aof the base 6 (cutting area) during the cutting operations. Therefore,the visibility of the cutting area and hence that of the marking line inthe cutting area is enhanced to consequently improve the efficiency ofthe cutting operation.

[0129] The fanned air that has struck the top surface of the cuttingobject then flows along the top surface of the cutting object into thegroove 6 c. The width of the groove 6 c with respect to the directionparallel to the rotary shaft of the saw blade 4 is smaller than thewidth of the opening 6 b, and the groove 6 c is formed such that a pairof imaginary lines extended in the cutting direction from theintersections of the lateral surfaces of the saw blade 4 and the bottomsurface 6 a of the base 6 locate within the groove 6 c. Therefore, thefanned air flown into the groove 6 c is directed in the cuttingdirection and discharged forward from the front end of the base 6. As aresult, the discharged fanned air blows off and prevents saw dust fromaccumulating on the cutting object in front of the base 6. Particularly,because the groove 6 c is located on the imaginary lines extended fromthe saw blade 4, the fanned air flows on the marking line drawn on thetop surface of the cutting object, blowing off saw dust from the markingline and improving the efficiency of the cutting operation.Additionally, since the groove 6 c has a sufficiently large width sothat the groove 6 c locates on the imaginary line extended from the sawblade 4 even when the saw blade 4 is tilted as described above, theinclined cutting operation also can be conducted efficiently.

[0130] Since the bottom surface of the guide piece 16 (FIG. 14) issubstantially flush with the top surface of the groove 6 c as describedabove, the fanned air that has flown into the groove 6 c can bedischarged from the front end of the base 6 without being blocked by theguide piece 16.

[0131] As described above, the boundaries of the upstream-side wallsurfaces of the flow rate reducing parts 5 dc 1 a-5 dc 3 a and those ofthe guiding parts 5 dc 1 b-5 dc 3 b of the division walls 5 dc 1-5 dc 3are not chamfered to show an arc-shaped profile, but are angular. If theboundaries are chamfered, the surface area of the flow rate reducingparts 5 dc 1 a-5 dc 3 a reduces so that fanned air will be dischargedinto the saw blade housing section 5 a through the fanned air dischargeports 5 c without sufficiently striking the flow rate reducing parts 5dc 1 a-5 dc 3 a. In this case, the fanned air is not sufficientlydecelerated, so that a large noise will be generated. However, in thisembodiment, such a problem is overcome by leaving the boundariesangular.

[0132] Because the fanned air discharge ports 5 c are defined by theplurality of division walls 5 d, the strength of the saw cover 5 issecured while securing the sufficient area of the fanned air dischargeports 5 c. Because all the division walls 5 d are formed to incline withrespect to the radial directions of the rotary shaft of the fan 7, thereinforcing effect of the division walls 5 d reduces. However, theguiding parts 5 dbb and 5 dc 1 b-5 dc 3 b, which are inclined relativeto the rotary shaft of the fan 7 and formed integrally with some of thedivision walls 5 d, enhances the reinforcing effect of the divisionwalls 5 d.

[0133] When the saw blade 4 is locked during the cutting operations,load is placed on the saw cover 5 via the bearings 11, 12, and 14,forcing the gear 9 and the pinion gear B to separate from each other.That is, the load is placed on the vicinity of the rotation center C1 ofthe fan 7 that is coaxial with the pinion gear 8 and also on thevicinity of the rotation center C2 of the saw blade 4 that is coaxialwith the gear 9. However, according to the present embodiment, as shownin FIG. 25, the division walls 5 dc 1-5 dc 3 having the guiding parts 5dc 1 b-5 dc 3 b are provided to these areas and improve thereinforcement effect particularly in these areas where relatively largeload is placed, improving the service life of the saw cover 5.

[0134] Because the fanned air discharge ports 5 c are arranged radiallyabout the rotation center C1 of the fan 7, the fanned air dischargedthrough any of the fanned air discharge ports 5 c strikes the lateralsurface of the saw blade 4 or the safety cover 17 and flows along thelateral surface into the opening 5 b, regardless of the cutting depth.Therefore, the efficiency of the cutting operation is improvedregardless of the cutting depth.

[0135] As described above, according to the present embodiment, thefanned air produced by the fan 7 cools the motor 1, flows through thegroove 6 c, and flows out from the front end of the base 1. The fannedair from the front end of the base 1 blows off dust from the top surfaceof the cutting object to prevent the dust from accumulating on themarking line on the cutting object. Thus, the marking line is preventedfrom being hid by dust and dirt that otherwise accumulate on the cuttingobject, and the cutting accuracy is improved. Because dust and dirt areblown off during the cutting operation, it is unnecessary to stop thecutting operation to remove the dust from the cutting object. In thismanner also, the efficiency of the cutting operation is improved.Further, because the fanned air is discharged from the opening at thefront end of the base 1 after passing through the groove 6 c formed inthe bottom surface 6 a of the base 6, it is unnecessary to provide aseparate guide pipe for guiding fanned air. Thus, the number ofcomponents is reduced to improve the efficiency of assembling and toreduce the cost. Also, such a guide pipe would not be obstacle tovisually confirm the positional relationship between the marking lineand the edge of the saw blade.

[0136] It should be noted that although the division walls 5 dc 1-5 dc 3of the present embodiment have the flow rate reducing parts 5 dc 1 a-5dc 3 a and the guiding parts 5 dc 1 b-5 dc 3 b, the division walls 5 dc1-5 dc 3 could only have the guiding parts 5 dc 1 b-5 dc 3 b. With thisconfiguration also, the fanned air can be discharged from the front endof the base 6 through the opening 6 b and the groove 6 c of the base 6.

[0137] It is possible to provide a member at the bottom surface 6 a ofthe base 6 for covering the groove 6 c as long as the fanned airdischarged into the opening 6 b can pass through the groove 6 c and blowforward from the front end of the base 6.

[0138] In this embodiment, the saw cover 5 is linked to the base 6, andthe housing 2 is linked to the base 6 via the saw cover 5. However, thepresent invention is not limited to this arrangement. For example, thehousing 2 could be directly linked to the base 6, or the base 6 could belinked to a member that is not movable relative to the housing 2.

[0139] Next, a portable electric circular saw according to a secondembodiment of the present invention will be described with reference toFIGS. 29-34. In this embodiment, the components that correspond to thoseof the first embodiment are denoted by the same reference symbols towhich “100” is added. For example, a housing 102, a handle 103, a sawcover 105, a saw blade housing section 105 a, fanned air discharge ports105 c, division walls 105 d, a base 106, an opening 106 b, a safetycover 117, and the like are shown in these drawings. While the fannedair flows forward in the cutting direction to the opening 6 b throughthe saw cover 5 in the first embodiment, the fanned air flows forward tothe opening 106 b along the outer wall of the saw cover 105 in thissecond embodiment as described later.

[0140] As shown in FIG. 29, a groove 106 c is formed in the bottomsurface 106 a of the base 106 to communicate with the opening 106 b. Thegroove 10 c extends from the front end of the opening 106 b to the frontend of the base 106 as viewed in the cutting direction. As in the firstembodiment, the groove 106 c is located on the imaginary line extendedin the cutting direction from the saw blade 4 and has a width greaterthan the thickness of the saw blade 4. The width of the groove 106 c islarge enough that the imaginary line extended in the cutting directionfrom the saw blade 4 is within the groove 106 c with respect to thewidthwise direction of the groove 106 c even when the saw blade 4 istilted by the maximum angle. In other words, the marking line on thecutting object locates within the groove 106 e with respect to thewidthwise direction of the groove 106 c even when the saw blade 4 istilted by the maximum degree. The base 106 is linked to the housing 102and/or the saw cover 105.

[0141] As shown in FIG. 31, an outer peripheral wall 105A is provided tothe saw cover 105 at the end close to the housing 102. The outerperipheral wall 105A includes a plurality of division walls 105 ddefining a plurality of fanned air discharge ports 105 c. As shown inFIG. 29, the division walls 105 d are tilting toward the base 106,particularly toward the cutting area within the opening 106 b The fannedair discharge ports 105 c are located at radially outward position withrespect to the rotary shaft of the fan 7 and separate from the fan 7with respect to the direction parallel to the rotary shaft of the fan 7.

[0142] As shown in FIGS. 31 and 32, a division wall 105 b is providedbetween the saw blade housing section 105 a and the housing 102 so as toseparate the saw blade housing section 105 a from the housing 102. Thedivision wall 105 b blocks and prevents fanned air W from flowing intothe saw blade housing section 105 a. The division wall 105 b has aninclined wall 105 j disposed near the fanned air discharge ports 105 c.The inclined wall 105 j is tilted toward the intersection of the bladeedge of the saw blade 4 and the bottom surface 106 a of the base 106,such that the distance between the inclined wall 105J and the lateralsurface of the saw blade 4 gradually decreases toward the radiallyoutward position with respect to the center of the fan 7. As shown inFIG. 32, a recess 105 m is formed in the front side of the saw cover 105as viewed in the cutting direction for allowing the fanned air W to passtherethrough.

[0143] With this configuration, the fanned air W entered inside theouter peripheral wall 105A hits the division wall 105 b and flows alongthe inclined wall surface 105 j toward the lateral surface of the sawblade 4. In this manner, the fanned air W is directed toward the opening106 b. Thereafter, the fanned air W passes through the fanned airdischarge ports 105 c and the recess 105 m and is discharged from thesaw cover 105 forward in the cutting direction (toward the right side inFIG. 30).

[0144] The fanned air W discharged to the outside of the saw cover 105further flows toward the opening 106 b of the base 106, strikes the topsurface of the cutting object in an area within the opening 106 b, andthen diffuses. Afterward, the fanned air W passes through the spacebetween the groove 106 c and the top surface of the cutting object, andthen the fanned air W is discharged from the front end of the base 106along the top surface of the cutting object. As a result, the fanned airW blows off and prevents dust from accumulating on the top surface ofthe cutting object in an area within the opening 106 b and also in anarea located at the front side of the base 106 as viewed in the cuttingdirection, improving the visibility of the marking line and theefficiency of cutting operation.

[0145] Because the division walls 10 d and thus the fanned air dischargeports 105 c are arranged so as to discharge the fanned air W forward asviewed in the cutting direction, the fanned air W will not be directedto the user during the cutting operation.

[0146] As described above, because the inclined wall surface 105 j isprovided to the saw cover 105 for guiding the fanned air toward theopening 106 c of the base 106, saw dust can be prevented effectivelyfrom accumulating on the cutting object without increasing the number ofcomponents.

[0147] Next, a portable electric circular saw according to a thirdembodiment of the present invention will be described with reference toFIG. 35. The portable electric circular saw of the third embodiment issimilar to the portable electric circular saw of the above-describedfirst embodiment or the second embodiment, but differs in a grooveformed in a base. As shown in FIG. 35, a base 206 of the presentembodiment is formed with a groove 206 c whose width with respect to thedirection parallel to the rotary shaft of the saw blade 4 increasestoward the saw blade 4 such that the housing-side edge of the groove 206c tilts toward the housing 202. Such a groove 206 c helps to directfanned air, which is discharged to a place closed to the housing 202,into the groove 206 c as much as possible. As shown in FIG. 35, theportable electric circular saw of the present embodiment includes aguide piece 216 having a vertical cutting guide section 216 a and a45-degree cutting guide section 216 b.

[0148] Here, the portable electric miter of the third embodiment couldbe modified so that the other side edge of the groove 206 c tiltsoutward toward the saw blade 4, that is, the edge tilts to the directionopposite to the housing 2 toward the saw blade 4. It is also possible toform the groove 206 c such that the depth of the groove 206 c increasestoward the opening 206 b. In this case, the upper wall of the groove 206c locates above the bottom surface 206 a of the base 206 at the positionclose to the opening 206 b. In these manner also, it is possible toincrease the amount of fanned air introduced into the groove 206 c.

[0149] Next, portable electric circular saws according to fourth throughsixth embodiments of the present invention will be described in thisorder. The portable electric circular saws of the fourth through sixthembodiments are any of the first through third embodiments provided withan air-blow regulating mechanism to be described later that regulatesthe amount of fanned air discharged forward from the front end of thebase. The air-blow regulating mechanism is particularly effective for aworking environment where dispersion or scattering of dust must beobviated. To this effect, in the fourth through sixth embodiments, theair-blow regulating mechanism is provided at a base.

[0150] First, the portable electric circular saw according to the fourthembodiment will be described in detail with reference to FIGS. 36 and37. The air-blow regulating mechanism includes a groove 306 f formed ina bottom surface 306S of a base 306, a shield member 351 formed with along through hole 351 a and housed in the groove 306 f, and a screw 352engaged with the base 306 through the hole 351 a. The groove 306 f isformed at the rear of a hole 306 d with respect to the cuttingdirection. The groove 306 f is in fluid communication with the groove306 c and has substantially the same depth as the groove 306 c. Theshield member 351 is slidable along the groove 306 f between anon-shielding position shown in FIG. 36 and a shielding position shownin FIG. 37. The screw 352 locks and unlocks the sliding position of theshield member 351 relative to the base 306. That is, the shield member351 is slidable within the length of the hole 351 a, and its position isfixed by tightening the screw 352.

[0151] When the shield member 351 is set to the non-shielding positionshown in FIG. 36, fanned air discharged toward the opening 306 b of thebase 306 can flow through the groove 306 c and blow forward from thefront end of the base 306 as viewed in the cutting direction in a mannerdescribed in the above embodiments, thereby preventing saw dust fromaccumulating. On the other hand, when the shield member 351 is set tothe shielding position shown in FIG. 37, the shield member 351 blocksthe groove 306 c so that the fanned air hits the shield member 351 andcannot pass through the groove 306 c. Therefore, the fanned air isprevented from blowing forward from the front end of the base 306,thereby preventing saw dust from being dispersed at the front end of thebase 306. In this manner, it is possible to selectively prevent thedispersion of saw dust as desired.

[0152] Further, if the user sets the shield member 351 at a positionbetween the shielding position and the non-shielding position, theamount of the fanned air discharged forward through the groove 306 c isregulated. That is, the user can utilize the blower mechanism whileminimizing the dispersion of saw dust.

[0153] As described above, according to the present embodiment, theair-blow regulating mechanism can regulate the amount of the fanned airthat blows out from the opening at the front end of the base, saw dustcan be prevented from being dispersed in a work site where dispersion ofsaw dust should be obviated. Also, it is possible to prevent saw dustfrom being accumulated on the marking line on the cutting object whileminimizing the dispersion of saw dust by decreasing the flow amount offanned air. Saw dust can be prevented selectively from being disperseddepending on the requirements of the work site.

[0154] Next, the portable electric circular saw according to the fifthembodiment of the present invention will be described with reference toFIGS. 38-40. An air-blow regulating mechanism according to the presentembodiment includes a male threaded hole 406 f formed in a base 406 at aposition corresponding to a groove 406 c, a shield member 451 formedwith a through hole 451 a, a screw 452 inserted into the through hole451 a and engaged with the male threaded hole 406 f, and a spring 453mounted around the screw 452. The shield member 451 has an L-shapedcross section and includes a support section that extends in thehorizontal direction and a shield section that extends in the verticaldirection. The shield member 451 has a width substantially equal to thewidth of the groove 406 c in a direction parallel to the rotary shaft ofthe fan 7 (in a direction perpendicular to the sheet of FIG. 38). Thespring 453 is interposed between the shield member 451 and the topsurface of the base 406 and urges the shield member 451 upwardly. Thebase 406 is formed with a through hole 406 d through which the shieldsection of the shield member 451 can pass. A user can slide the shieldmember 451 upward and downward between a non-shielding position shown inFIG. 38 and a shielding position shown in FIG. 40 by turning the screw452.

[0155] When the shield member 451 is set to the non-shielding positionshown in FIG. 38, fanned air can flow through the groove 406 c formed ina bottom surface 406 a of the base 406 and blow forward in the cuttingdirection from the base 406. On the other hand, when the shield member451 is set to the shielding position shown in FIG. 40, then fanned airstrikes the shield member 451 and hence cannot be directed forward inthe cutting direction. Therefore, the fanned air is not introduced intothe groove 406 c and prevented from blowing out forward from the frontend of the base 406. In this manner, saw dust is prevented from beingdispersed during the cutting operation.

[0156] Further, when the shield member 451 is set to a regulatingposition shown in FIG. 39, the amount of fanned air that is dischargedforward from the base 406 is decreased. Therefore, saw dust is preventedfrom accumulating on the marking line while minimizing the dispersion ofsaw dust.

[0157] Next, the portable electric circular saw according to the sixthembodiment of the present invention will be described with reference toFIGS. 41-44. The portable electric circular saw according to the presentembodiment includes a guide piece 516 equipped with the air-flowregulating mechanism. As shown in FIGS. 41 and 43, the guide piece 516has a non-shield side 516A and a shield side 516B and is detachablyfitted to the top surface of a base 506 by a screw 18. Usually, theguide piece 516 is fitted to the base 506 with the non-shield side 516Afacing downward as shown in FIG. 41. However, when the blower mechanismis not used, the guide piece 516 is turned upside down and fitted to thebase 506 with the shield side 516B facing downward as shown in FIG. 43.

[0158] The non-shield side 516A of the guide piece 516 is provided withguide sections 516 a and 516 b. The guide section 516 a is forindicating the edge position of the saw blade 4 when the saw blade 4 isin the upright posture. The guide section 516 b is for indicating theedge position of the saw blade 4 when the saw blade 4 is tilted by themaximum angle of 45 degree. Projections 516 a 1 and 516 b 1 areprojecting from the bottom surfaces of guide sections 516 a and 516 b,respectively, and extend in the cutting direction, thereby defininggrooves 516 c between and both sides of the guide sections 516 a and 516b. When the guide piece 516 is fitted to the base 506 with thenon-shield side 516A facing downward as shown in FIG. 41, theprojections 516 a 1 and 516 b 1 reach the level substantially equal to(flush with) the bottom surface 506 a of the base 506.

[0159] On the other hand, the shield side 516B of the guide piece 516 isprovided with guide sections 516 d and 516 e. The guide section 516 b isfor indicating the edge position of the saw blade 4 when the saw blade 4is in the upright posture. The guide section 516 e is for indicating theedge position of the saw blade 4 when the saw blade 4 is tilted by themaximum angle of 45 degree. A shield section 516 h is disposed to theshield side 516B of the guide piece 516. The shield section 516 h has awidth substantially equal to the width of the groove 506 c. When theguide piece 516 is fitted to the base 506 with the shield side 516Bfacing downward as shown in FIG. 42, the shield section 516 h reachesthe level substantially equal to the bottom surface 506 a of the base506.

[0160] With this configuration, when the guide piece 516 is fitted tothe base 506 with the non-shield side 516A facing downward as shown inFIG. 41, fanned air flows through the grooves 506 c and 516 c and blowsfrontward from the front end of the base 506. On the other hand, whenthe guide piece 516 is fitted to the base 506 with the shield side 516Bfacing downward as shown in FIG. 43, the shield section 516 h blocks thefanned air and prevents the same from passing through the groove 506 c,so that the fanned air is not discharged from the front end of the base506. In this manner, the blower mechanism can be turned ON and OFF byselecting the side of the guide piece 516 to fit to the base 506. Here,the guide piece 516 is fitted to the base 506 by the screw 18, which isinserted through either one of a through hole 516 f and a hole 516 g.The through hole 516 f is used when the non-shield side 516A is faceddownward, and the through hole 516 g is used when the shield side 516Bis faced downward.

[0161] Next, portable electric circular saws according to seventh toninth embodiments of the present invention will be described in thisorder. The portable electric circular saws according to theseembodiments each includes an air-blow regulating mechanism provided to asaw cover.

[0162] First, the portable electric circular saw according to theseventh embodiment will be described with reference to FIGS. 45-48. Theportable electric circular saw is similar to that of the firstembodiment, but differs in including the air-blow regulating mechanism.The air-blow regulating mechanism includes a shield member 651 slidableup and down along the step 5 g that is formed on the saw cover 5 toextend in the vertical direction. The shield member 651 is formed toL-shape having a step sliding section 651A and a saw-cover slidingsection 651B. The step sliding section 651A contacts and slides alongthe step 5 g, and the saw-cover sliding section 651B contacts and slidesalong the saw cover 605. A saw cover 605 is formed with a verticallyextending slot 605 k (FIGS. 47 and 48). A screw 652 is inserted throughthe slot 605 k and engaged with the saw cover sliding section 651B. Withthis configuration, the shield member 651 can slides up and down withinthe length of the slot 605 k, and the position of the shield member 651is secured by tightening the screw 652.

[0163] When the screw 652 abuts the top end of the slot 605 k as shownin FIG. 45, the shield member 651 is placed to a non-shielding positionthat is the top position. In this case, fanned air flows toward theopening 6 b of the base 6, forward in the cutting direction, after orwithout striking the step sliding section 651A of the shield member 651.Accordingly, the fanned air can blow out from the front end of the base6 after passing through the groove 6 c.

[0164] On the other hand, when the screw 652 abuts the bottom end of theslot 605 k as shown in FIG. 46, the shield member 651 is in a shieldingposition that is the bottom position. In this case, fanned air directedtoward the opening 6 b strikes the shield member 651 so that the fannedair cannot flow forward in the cutting direction. Therefore, the fannedair does not enter the groove 6 c, and thus the fanned air is notdischarged from the front end of the base 606.

[0165] Further, when the shield member 651 is posited between thenon-shielding position and the shielding position, then the amount offanned air discharged forward from the front end of the base 606 isregulated. Accordingly, saw dust can be prevented from accumulating onthe marking line on the cutting object while minimizing the dispersionof saw dust.

[0166] Here, because the step 5 g guides the shield member 651 when theshield member 651 slides up and down, only a single screw 652 cansufficiently secure the shield member 651 in position.

[0167] Next, the portable electric circular saw according to the eighthembodiment of the present invention will be described with reference toFIGS. 49-52. The portable electric circular saw is similar to that ofthe seventh embodiment, but differs in a direction in which a shieldmember slides.

[0168] Specifically, the air-blow regulating mechanism of the presentembodiment includes a shield member 751 that is slidable forward andrearward in the cutting direction along the surface of a saw cover 705.The shield member 751 is in a substantially quadrilateral shape having afirst side substantially parallel to a step 705 g, a second sidesubstantially perpendicular to the first side, a third sidesubstantially parallel to the second side, and a fourth side in anarc-shape following the radially outer edges of the division walls 5d-As shown in FIGS. 50-52, the saw cover 705 is formed with a pair ofslots 705 k, 705 k extending substantially parallel to the cuttingdirection. A pair of screws 752 are inserted through the correspondingslots 705 k, 705 k and engaged with the shield member 751. With thisconfiguration, the shield member 751 can slide to the front and to therear within the length of the slots 705 k, and the position of theshield member 751 is secured by tightening the screws 752.

[0169] When the screws 752 abut the front ends of the slots 705 k asshown in FIG. 49, the shield member 751 is at a non-shielding position.In this case, the fanned air discharge ports 5 c are fully openedwithout being blocked by the shield member 751, and therefore fanned aircan be directed forward toward the opening 6 b of the base 6 in thecutting direction. Accordingly, the fanned air can be discharged fromthe front end of the base 6 after passing through the groove 6 c.

[0170] On the other hand, when the screws 752 abut the left ends of theslots 705 k as shown in FIG. 50, the shield member 751 is at a shieldingposition. In this case, the shield member 751 closes most parts of thefanned air discharge ports 5 c. Therefore, fanned air is not directedfrontward, that is, to the groove 6 c, and is prevented from blowing outforward from the front end of the base 6. When the shield member 751 ispositioned between the non-shielding position and the shieldingposition, then the amount of fanned air discharged forward from the base706 is regulated.

[0171] Next, the portable electric circular saw according to the ninthembodiment of the present invention will be described with reference toFIGS. 53-55. The portable electric circular saw of the presentembodiment is similar to that of the second embodiment, but differs inincluding the air-blow regulating mechanism.

[0172] The air-blow regulating mechanism includes a shield member 851slidably disposed on the outer surface of an outer wall 805A at thefront side of the saw cover 805 as viewed in the cutting direction. Morespecifically, the shield member 851 is formed with a verticallyextending slot 851 a, and a screw 852 is inserted through the slot 851 aand engaged with the outer wall 805A.

[0173] When the screw 852 is in abutment with the bottom end of the slot851 a as shown in FIG. 53, the shield member 851 is in a non-shieldingposition that is the top position. In this case, a recess 805 m formedat the front side of the saw cover 805 is not covered by the shieldmember 851. Therefore, fanned air discharged from fanned air dischargeports 805 c can pass through the recess 805 m, flow forward toward thebase opening 6 b, and blow out from the front end of the base 6 afterpassing through the groove 6 c.

[0174] On the other hand, when the screw 852 is in abutment with the topend of the slot 851 a as shown in FIG. 54, the screw 852 is in ashielding position that is the bottom position. In this case, the shieldmember 851 covers the recess 805 m and therefore, the fanned air Wdischarged from the fanned air discharge ports 805 c is blocked by theshield member 851 and thus prevented from flowing into the groove 6 c ofthe base 6. Accordingly, the fanned air is prevented from dischargedfrom the front end of the base 6.

[0175] When the shield member 751 is positioned between thenon-shielding position and the shielding position, then the amount offanned air discharged forward from the base 706 is regulated.

[0176] While some exemplary embodiments of this invention have beendescribed in detail, those skilled in the art will recognize that thereare many possible modifications and variations which may be made inthese exemplary embodiments while yet retaining many of the novelfeatures and advantages of the invention.

What is claimed is:
 1. A portable electric cutting device comprising: asaw blade that cuts a cutting object in a cutting direction; a casingthat partially houses the saw blade; and a base linked to the casing,the base having a bottom surface that slides on the cutting object, thebottom surface being formed with an opening through which the saw bladeprojects downward beyond the bottom surface, the bottom surface beingformed with a first groove extended forward in the cutting directionfrom a front end of the opening to a front end of the base, the firstgroove being in fluid communication with the opening and being opened tothe front end of the base.
 2. The portable electric cutting deviceaccording to claim 1, further comprising a guide piece removablyattached to the front end of the base for indicating a position of ablade edge of the saw blade, the guide piece having a bottom surfaceformed with a second groove that is in fluid communication with thefirst groove.
 3. The portable electric cutting device according to claim1, wherein the partition wall of the saw cover is further formed with astep at a first side, the step having a lower end that is located rearof the opening formed in the base with respect to the cutting direction.4. The portable electric cutting device according to claim 3, furthercomprising a light irradiation device that irradiates the front end ofthe base and the cutting object in an area in front of the base in thecutting direction, wherein the partition wall of the saw cover isfurther formed with a recess at a second side opposite to the firstside, and the step of the partition wall is formed as a result offorming the recess, the recess having a flat section extending inparallel with the saw blade, and the light irradiation device isattached to the flat portion of the recess.
 5. The portable electriccutting device according to claim 1, wherein the first groove is locatedon an imaginary line extended in the cutting direction from the sawblade and has a width greater than a thickness of a blade edge of thesaw blade.
 6. The portable electric cutting device according to claim 5,further comprising a tilting mechanism arranged between the saw coverand the base, the tilting mechanism tilting the saw cover by a desiredangle and supporting the saw cover at the desired angle, wherein thefirst groove is located on the imaginary line even when the saw blade istilted by a maximum angle.
 7. The portable electric cutting deviceaccording to claim 1, further comprising a cutting depth regulatingmechanism, wherein the saw cover is connected to the base at front andrear sides of the base, the saw cover being pivotable about a front endof the saw cover with respect to the base, and the cutting depthregulating mechanism is disposed between the rear side of the base andthe saw cover for regulating a cutting depth by pivoting the saw coverabout the front end of the saw cover relative to the base such that arear end of the saw cover moves up and down, the cutting depthregulating mechanism supporting the saw cover at a desired position withrespect to a pivotal direction of the saw cover.
 8. The portableelectric cutting device according to claim 1, further comprising areinforcement member disposed on a top surface of the base, thereinforcement member extending between an area vertically above thefirst groove and an area vertically above where the first groove is notformed.
 9. The portable electric cutting device according to claim 8,further comprising a tilting mechanism disposed between the saw coverand the front side of the base for tilting the saw cover by a desiredangle with respect to a vertical direction and for supporting the sawcover at the desired angle, the tilting mechanism having a pin aboutwhich the saw cover tilts, the pin being held by the reinforcementmember.
 10. The portable electric cutting device according to claim 9,wherein the tilting mechanism further has a bevel plate projectingupward from the base and being formed with an arc-shaped hole centeredat the pin and a locking screw engaged with the saw cover at a front endthrough the arc-shaped hole, the locking screw securing the saw cover atthe desired angle when tightened, and the reinforcement member is linkedto the bevel plate.
 11. The portable electric cutting device accordingto claim 1, further comprising a fan that generates an air current asfanned air, wherein the casing includes a housing that houses the fanand a saw cover that includes a saw blade housing section that partiallyhouses the saw blade, and the saw cover has a partition wall disposedbetween the fan and the saw blade housing section, the partition wallbeing formed with a plurality of division walls defining a plurality ofdischarge ports through which the fanned air generated inside thehousing is discharged forward in the cutting direction toward theopening formed in the base, wherein the first groove is an air-passinggroove.
 12. The portable electric cutting device according to claim 11,further includes a motor that drives both the saw blade and the fan torotate, the fan generates the fanned air to cool the motor.
 13. Theportable electric cutting device according to claim 11, wherein: the fanrotates in a rotary direction to generate the fanned air; each of theplurality of division walls extends from a fan side to asaw-blade-housing-section side and has an upstream-side surface at anupstream side in the rotary direction of the fan; at least one of thedivision walls is a first division wall that has an inclined part whoseupstream-side surface is inclined with respect to a rotary axis of thefan such that a saw-blade-housing-section-side section of theupstream-side surface locates downstream of a fan-side section of theupstream-side surface with respect to the rotary direction of the fan;and the fanned air generated inside the housing is discharged throughthe discharge ports into the saw blade housing section of the saw cover.14. The portable electric cutting device according to claim 13, whereineach of the division walls has a downstream-side surface opposite to theupstream-side surface, the downstream-side surface being substantiallyparallel to the corresponding upstream-side surface.
 15. The portableelectric cutting device according to claim 13, wherein the firstdivision wall is located at front side of the rotary axis of the fanwith respect to the cutting direction.
 16. The portable electric cuttingdevice according to claim 13, wherein the first division wall has a flowrate reducing part whose upstream-side surface extends substantiallyparallel to the rotary axis of the fan, the flow rate reducing partbeing disposed at the fan side whereas the inclined part is disposed atthe saw-blade-housing-section side, wherein the inclined part is aguiding part extending at an angle with respect to the upstream-sidesurface of the flow rate reducing part.
 17. The portable electriccutting device according to claim 16, wherein the flow rate reducingpart is connected to the guiding part, and a boundary between the flowrate reducing part and the guiding part is in an angular shape withoutbeing chamfered.
 18. The portable electric cutting device according toclaim 16, wherein each division wall has a first end at thesaw-blade-housing-section side and a second end at the fan side oppositeto the first end, and the first end of the first division wall and thesecond end of an adjacent division wall located to the downstream sideof the first division wall with respect to the rotary direction define agap therebetween, the gap extending through the partition wall in adirection substantially parallel to the rotary axis of the fan.
 19. Theportable electric cutting device according to claim 18, wherein the gapis defined between the upstream-side surface of one first division walland the downstream-side surface of another first division wall adjacentto the one first division wall, the upstream-side surface of the onefirst division wall and the downstream-side surface of the another firstdivision wall extend substantially in parallel with each other.
 20. Theportable electric cutting device according to claim 13, wherein at leastone of the division walls is a second division wall located at rear sideof the rotation axis of the fan with respect to the cutting direction,the upstream-side surface of each second division wall extends parallelto the rotation axis of the fan.
 21. The portable electric cuttingdevice according to claim 13, wherein the upstream-side surface of atleast one division wall extends at an angle with respect to a radialdirection of a rotary shaft of the fan such that a radially outer partof the upstream-side surface locates upstream from a radially inner partof the upstream-side surface with respect to the rotary direction of thefan.
 22. The portable electric cutting device according to claim 21,wherein the upstream-side surface of any of the division wall extends atan angle with respect to the radial direction of the rotary shaft of thefan such that a radially outer part of the upstream-side surface locatesupstream from a radially inner part of the upstream-side surface withrespect to the rotary direction of the fan.
 23. The portable electriccutting device according to claim 21, wherein the upstream-side surfaceof any of the division walls extends at the angle of 45 degree relativeto the radial direction of the rotary shaft of the fan.
 24. The portableelectric cutting device according to claim 11, wherein the saw coverfurther includes another partition wall disposed between the housing andthe saw cover housing section, the another partition wall extending atan angle with respect to the cutting direction such that the anotherpartition wall is closer to the saw blade toward a radially outer endwith respect to a radial direction of a rotary shaft of the fan.
 25. Theportable electric cutting device according to claim 24, wherein thedivision walls extend toward the opening formed in the base.
 26. Theportable electric cutting device according to claim 11, furthercomprising an air-blow regulating mechanism that selectively regulatesthe amount of fanned air that is discharged from the front end of thebase through the first groove.
 27. The portable electric cutting machineaccording to claim 26, wherein the air-blow regulating mechanism isprovided to the base.
 28. The portable electric cutting machineaccording to claim 27, wherein: the bottom surface of the base isfurther formed with a guide groove that is in fluid communication withthe first groove, the guide groove having substantially the same depthas the first groove; and the air-blow regulating mechanism includes ashield member that is disposed in the guide groove, the shield memberbeing slidable along the guide groove between a shield position wherethe shield member closes the first groove and a non-shield positionwhere the shield member opens the first groove.
 29. The electricportable cutting device according to claim 28, wherein the air-blowregulating mechanism further includes a fixing member that selectivelyfixes and releases the shield member to and from a desired position. 30.The electric portable cutting device according to claim 26, wherein: thebase is formed with a guide hole penetrating through the base, the guidehole being in fluid communication with the first groove; the air-blowregulating mechanism includes a shield member and a positioning member;the shield member is inserted into the guide hole and slides along theguide hole between a shield position where the shield member closes thefirst groove and a non-shield position where the shield member opens thefirst groove; and the positioning member supports the shield member andpositions the shield member to a desired position.
 31. The electricportable cutting device according to claim 26, wherein: the air-blowregulating mechanism includes a shield member and an attaching member,the shield member having a shield side and a non-shield side, theattaching member detachably attaches the shield member to the baseselectively with the shield side facing toward the bottom surface of thebase and with the non-shield side facing toward the bottom surface ofthe base; the shield member has a shield portion disposed on the shieldside that closes the first groove when the shield member is attached tothe base with the shield side facing toward the bottom surface, theshield portion having a width substantially equal to a width of thefirst groove with respect to a direction perpendicular to the cuttingdirection; and the shield member is formed with a third groove at thenon-shield side, the third groove being in fluid communication with thefirst groove when the shield member is attached to the base with thenon-shield side facing toward the bottom surface, allowing the fannedair to pass through the third groove and the first groove.
 32. Theportable electric cutting device according to claim 24, wherein theair-blow regulating mechanism is provided to the saw cover.
 33. Theportable electric cutting device according to claim 32, wherein: the sawcover includes a protruding member that protrudes toward the saw blade,the protruding member being formed with a slot extending in a directionperpendicular to the cutting direction; the air-blow regulatingmechanism includes a shield member that slides along the slot between ashield position on an air path through which the fanned air isintroduced into the first groove and a non-shield position off of theair path, wherein the shield member at the shield position prevents thefanned air from entering the first groove; and the shield member has aL-shaped cross section having a first sliding part that slides along theprotruding member and a second sliding part that slides along the sawcover.
 34. The portable electric cutting device according to claim 33,wherein the air-blow regulating mechanism further includes a fixingmember that selectively fixes and releases the shield member to and froma desired position.
 35. The portable electric cutting device accordingto claim 32, wherein the saw cover is formed with a slot extending inthe cutting direction, and the air-blow regulating mechanism includes ashield member that slides along the slot between a shield position wherethe shield member covers the fanned air discharge ports and a non-shieldposition where the shield member uncovers the fanned air dischargeports.
 36. The portable electric cutting device according to claim 35,wherein the air-blow regulating mechanism further includes a fixingmember that selectively fixes and releases the shield member to and froma desired position.
 37. The portable electric cutting device accordingto claim 32, wherein: the saw cover is formed with a recess throughwhich the fanned air is directed to the first groove; the saw cover isformed with a slot; and the air-blow regulating mechanism includes ashield member that slides along the slot between a shield position wherethe shield member closes the recess and a non-shield position where theshield member opens the recess.
 38. The portable electric cutting deviceaccording to claim 37, wherein the air-blow regulating mechanism furtherincludes a fixing member that selectively fixes and releases the shieldmember to and from a desired position.